Gas purification techniques

Semi Dry Lime absorption

At semi dry lime absorption acid components such as HCl, HF and especially SO2 smoke gases are removed by putting it in contact with the carrier fluid in which reactant have been solved or are in suspension. A dry response product arises, so that there no supplies needed for carrier water treatment. To spray the carrier fluid very fine in the industrial gas, a large contact area is obtained between the gaseous pollution and the reactant in the carrier fluid. By absorption of the gaseous pollution in the drops, followed by a reaction between reactant and pollution, there a connection arises as a result of chemical absorption in the drop. Due to the high temperature of the smoke gases water evaporates, that's why the formed connection remains as a fixed substance. Such responses can be carried out with acid pollutions such as SO2, HCl and HF.


As reactants Ca(OH)2, CaCO3 and alternatives are used. Due to the large contact area a good output is possible with a small excess to chemicals.
Pollution, that is present after the reaction in the smoke gasses in solid form, can be removed by for example a thin filter material or a E-filter from the smoke gasses. At this cleansing at the same time the dust can be separated from the smoke gases . As a result of the vaporization of the carrier fluid the temperature of the
smoke gases has considerably decreased, therefore application of a thin filter material as a dust remover is possible.

The advantages at this process are:

  • higher dissidence degree regarding to dry lime absorption

  • relatively simple installation

  • cheaper than wet gas scrubbing

  • no effluent

The disadvantages are:

  • fought can it be unpleasant when thin filter material become placed in series

  • Remaining dust with excess lime

The application of this technique much are used in the detritus
combustion installations and electricity production.

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